Abstract Individuals on the autism spectrum experience a ?services cliff? when they transition to adulthood, and have poor health and social outcomes over the life course. In response, the National Institute of Mental Health has highly prioritized services research to improve life outcomes for autistic adults. The lack of validated patient- reported outcome measures (PROMs) for use with autistic adults is a significant barrier to conducting high- quality services research with this population. The Academic Autism Spectrum Partnership in Research and Education (AASPIRE) has been conducting community based participatory research (CBPR) in partnership with autistic adults, family members, and services professionals for over twelve years. We have used a collaborative process to adapt survey instruments to be accessible to autistic adults with diverse characteristics. More work is needed to create a full package of high-priority PROMs and to rigorously assess their psychometric properties. Our long-term goal is to improve life outcomes for autistic adults. The objective of this proposal is to use a CBPR approach to create and test a package of PROMs for evaluating the effectiveness of services interventions for autistic adults across multiple real-world settings. We will achieve our objective by meeting the following specific aims: 1) to collaboratively create the Autism Patient Reported Outcomes Measures (AutPROM) Toolbox; 2) to psychometrically test the AutPROM Toolbox measures at baseline and assess expected distributions; and 3) to assess the instruments? sensitivity in detecting change and explore factors that may be associated with change in outcomes over time. We will use a modified Delphi process to identify constructs and measures to include in the AutPROM Toolbox. We will then work with our diverse Community Council to collaboratively adapt instruments, as needed. Where appropriate, we will create two versions of each measure ? one for use by autistic adults and one for use by proxies. We will conduct cognitive interviews to establish content validity and comprehensibility of the adapted instruments. We will then test the full AutPROM Toolbox in a real-world cohort of 750 autistic adults, with sub-cohorts recruited from 1) healthcare systems; 2) disability services systems; and 3) community organizations. We will conduct surveys with participants at baseline and 6 and 12 months, and will use longitudinal growth curve modeling to test change over time and identify participant characteristics that are associated with changes in outcomes. We will use qualitative methods to understand how changes in scores on AutPROM Toolbox instruments correspond to participants? narratives of how their life may have changed during the study period. The proposed project will create a critically-needed set of PROMs that can be used to evaluate services interventions for autistic adults across multiple real-world settings. The project will also identify factors that predict changes in life outcomes over time. Such information is key to understanding and improving existing services, refining and targeting new interventions, and informing policy.